1. Field of the Invention
The present invention relates to an image display apparatus using an electron-emitting device.
2. Background Art
In a flat display in which: a large number of electron-emitting devices are arranged as electron sources on a flat substrate; a phosphor as an image forming member on an opposing substrate is irradiated with electron beams emitted from the electron sources; and the phosphor is allowed to emit light to display an image, the inside of a vacuum container including the electron sources and the image forming member must be kept at a high vacuum. When a gas is generated in the vacuum container to increase the pressure in the container, the increase adversely affects the electron sources to reduce an electron emission amount, thereby making it impossible to display a clear image, although the degree of the adverse effect varies depending on the kind of the gas.
In particular, the following problems are characteristic of a flat display. A gas generated from an image display member accumulates near an electron source before it reaches a getter placed outside an image display area, so a local increase in pressure and the deterioration of the electron source incidental to the local increase occur. Japanese Patent Application Laid-Open No. H09-82245 describes that a getter is arranged in an image display area to immediately adsorb a generated gas, thereby suppressing the deterioration and breakage of a device. Japanese Patent Application Laid-Open No. 2000-133136 describes a structure in which a non-evaporable getter is arranged in an image display area and a evaporable getter is arranged outside the image display area. Furthermore, Japanese Patent Application Laid-Open No. 2000-315458 proposes that a series of operations consisting of degassing, getter formation, and seal bonding (making a vacuum container) are performed in a vacuum chamber.
Getters are classified into a evaporable getter and a non-evaporable getter. The evaporable getter shows an extremely large exhaust velocity with respect to water or oxygen. However, each of the evaporable getter and the non-evaporable getter shows an exhaust velocity close to zero with respect to an inert gas such as argon (Ar). An argon gas is ionized by an electron beam to generate a plus ion. The plus ion is accelerated in an electric field for accelerating an electron to be bombarded with an electron source, thereby damaging the electron source. Furthermore, the argon ion may cause discharge inside an apparatus to break the apparatus.
Meanwhile, Japanese Patent Application Laid-Open No. H05-121012 describes a method involving connecting a sputter ion pump to a vacuum container of a flat display to maintain a high vacuum for a long period of time. However, the method requires a strong magnet, so the electron trajectory of the display is curved in a magnetic field to affect an image.